1. Field Of The Invention
The present invention relates to electrostatic spray coating systems and more particularly to electrostatic spray coating systems for applying conductive coatings such as water base paints.
2. Description Of The Prior Art
In the past years the applicant of the invention herein described designed and placed on the market automatic electrostatic spray coating systems for spraying highly conductive coatings such as porcelain enamel frit in a water carrier wherein the entire spray coating system including the entire supply system was electrically isolated from ground.
Such a system is disclosed in U.S. Pat. No. 3,463,121 issued Aug. 26, 1969, U.S. Pat. No. 3,621,815 issued Nov. 23, 1971 and U.S. Pat. No. 3,637,420 issued Jan. 25, 1972. Although such a system advanced the art, it could not have its main coating material supply reservoir filled while the high voltage was being applied to the system and it could not be utilized for manual spray systems for the operator would be touching components charged to the high voltage utilized in such systems.
Voltage blocks have been developed which consist of a main supply source of first container which is used to fill a second container. A third container at high voltage receives conductive coating material from the second container at times when no material is flowing from the first to the second container. These systems have the disadvantage that arcing will occur if insulated conduit is used between the first and second containers because of residual material on the conduit surfaces. Pouring from a transportation drum or container, as the grounded first container eliminates this arcing, but there still remains three required sub-systems which are the first at ground, the second or intermediate alternately at ground or high voltage, and the third at high voltage. Further, these three container or three sub-system supply systems can not be utilized for manual electrostatic spray systems for the operator would be touching components charged to high voltage.